The proposed study will investigate the relation between environmental exposures in susceptible hosts and the subsequent risks for development acute lymphatic leukemia (ALL) and non-Hodgkin's lymphomas (NHL) among children less than 16 years of age. The investigation will focus upon multiple exposures, both environmental and biologic, in the lives of the index subjects themselves, as well as the lives of their parents prior to the index subject's birth. The primary investigation will utilize laboratory and epidemiologic techniques to characterize cases/controls and in some instances, members of their families, to test the following hypotheses: 1) To determine if family members of patients with particular immunologic subsets of acute lymphoblastic leukemia or non-Hodgkin's lymphoma, specifically B or pre-B (antibody producing) cell disease have a high incidence of autoimmune phenomena than families of matched controls. In addition to ascertaining family histories of clinically apparent autoimmune disease, specific cellular and serum determinations will be made including: fluorescent antinuclear antibody(FANA), quantitation of suppressor and helper T-cells and complement levels. 2) To assess if there exists an association between specific environmental exposures and chromosomal abnormalities in the leukemia cases through a comparison of exposed cases with nonexposed cases. Cytogenetic information will be ascertained from banded karyotype studies of diagnostic bone marrow samples. 3) Molecular hybridization techniques will be utilized to determine the presence of BLV particles in the marrow of cases only and the peripheral blood of the cases and controls. DNA hybridization studies of cases will be performed on pretreatment specimens. 4) To determine the pattern of enteraction between environmental exposures and host characteristics. Epidemiologic factors include ionizing radiation, animals, occupational exposures of parents and disease histories of family members including parents, siblings, and grandparents. Quantification of the risks associated with these exposures will be made by contrasting the cases of acute lymphoblastic leukemia and non-Hodgkin's lymphomas to a set of age-, sex-, and race-matched regional population controls.